diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index e32ff71..c25777f 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -6,6 +6,7 @@
 
 - dtmt: split `build` into `build` and `package`
 - dtmt: implement deploying built bundles
+- dtmm: indicate when a deployment is necessary
 
 == 2023-03-01
 
diff --git a/crates/dtmm/src/controller/app.rs b/crates/dtmm/src/controller/app.rs
index b9903cf..aba2442 100644
--- a/crates/dtmm/src/controller/app.rs
+++ b/crates/dtmm/src/controller/app.rs
@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::io::{Cursor, ErrorKind, Read};
 use std::path::Path;
+use std::sync::Arc;
 
 use color_eyre::eyre::{self, Context};
 use color_eyre::{Help, Result};
@@ -107,7 +108,7 @@ pub(crate) async fn import_mod(state: State, info: FileInfo) -> Result<ModInfo>
 
     let packages = files
         .into_iter()
-        .map(|(name, files)| PackageInfo::new(name, files.into_iter().collect()))
+        .map(|(name, files)| Arc::new(PackageInfo::new(name, files.into_iter().collect())))
         .collect();
     let info = ModInfo::new(mod_cfg, packages);
 
@@ -171,14 +172,14 @@ async fn read_mod_dir_entry(res: Result<DirEntry>) -> Result<ModInfo> {
 
     let packages = files
         .into_iter()
-        .map(|(name, files)| PackageInfo::new(name, files.into_iter().collect()))
+        .map(|(name, files)| Arc::new(PackageInfo::new(name, files.into_iter().collect())))
         .collect();
     let info = ModInfo::new(cfg, packages);
     Ok(info)
 }
 
 #[tracing::instrument(skip(mod_order))]
-pub(crate) fn load_mods<'a, P, S>(mod_dir: P, mod_order: S) -> Result<Vector<ModInfo>>
+pub(crate) fn load_mods<'a, P, S>(mod_dir: P, mod_order: S) -> Result<Vector<Arc<ModInfo>>>
 where
     S: Iterator<Item = &'a LoadOrderEntry>,
     P: AsRef<Path> + std::fmt::Debug,
@@ -214,7 +215,7 @@ where
             .filter_map(|entry| {
                 if let Some(mut info) = mods.remove(&entry.id) {
                     info.enabled = entry.enabled;
-                    Some(info)
+                    Some(Arc::new(info))
                 } else {
                     None
                 }
diff --git a/crates/dtmm/src/controller/worker.rs b/crates/dtmm/src/controller/worker.rs
index 80abf53..49785b4 100644
--- a/crates/dtmm/src/controller/worker.rs
+++ b/crates/dtmm/src/controller/worker.rs
@@ -41,7 +41,7 @@ async fn handle_action(
                             .await
                             .submit_command(
                                 ACTION_FINISH_ADD_MOD,
-                                SingleUse::new(mod_info),
+                                SingleUse::new(Arc::new(mod_info)),
                                 Target::Auto,
                             )
                             .expect("failed to send command");
diff --git a/crates/dtmm/src/state/data.rs b/crates/dtmm/src/state/data.rs
index c8dc3aa..65156a3 100644
--- a/crates/dtmm/src/state/data.rs
+++ b/crates/dtmm/src/state/data.rs
@@ -17,7 +17,7 @@ impl Default for View {
     }
 }
 
-#[derive(Clone, Data, Debug)]
+#[derive(Clone, Data, Debug, PartialEq)]
 pub struct PackageInfo {
     pub name: String,
     pub files: Vector<String>,
@@ -29,14 +29,14 @@ impl PackageInfo {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 pub(crate) struct ModResourceInfo {
     pub init: PathBuf,
     pub data: Option<PathBuf>,
     pub localization: Option<PathBuf>,
 }
 
-#[derive(Clone, Data, Debug, Lens)]
+#[derive(Clone, Data, Debug, Lens, PartialEq)]
 pub(crate) struct ModInfo {
     pub id: String,
     pub name: String,
@@ -44,14 +44,14 @@ pub(crate) struct ModInfo {
     pub enabled: bool,
     #[lens(ignore)]
     #[data(ignore)]
-    pub packages: Vector<PackageInfo>,
+    pub packages: Vector<Arc<PackageInfo>>,
     #[lens(ignore)]
     #[data(ignore)]
     pub resources: ModResourceInfo,
 }
 
 impl ModInfo {
-    pub fn new(cfg: ModConfig, packages: Vector<PackageInfo>) -> Self {
+    pub fn new(cfg: ModConfig, packages: Vector<Arc<PackageInfo>>) -> Self {
         Self {
             id: cfg.id,
             name: cfg.name,
@@ -67,17 +67,12 @@ impl ModInfo {
     }
 }
 
-impl PartialEq for ModInfo {
-    fn eq(&self, other: &Self) -> bool {
-        self.name.eq(&other.name)
-    }
-}
-
 #[derive(Clone, Data, Lens)]
 pub(crate) struct State {
     pub current_view: View,
-    pub mods: Vector<ModInfo>,
+    pub mods: Vector<Arc<ModInfo>>,
     pub selected_mod_index: Option<usize>,
+    pub dirty: bool,
     pub is_deployment_in_progress: bool,
     pub is_reset_in_progress: bool,
     pub is_save_in_progress: bool,
@@ -106,6 +101,7 @@ impl State {
             current_view: View::default(),
             mods: Vector::new(),
             selected_mod_index: None,
+            dirty: false,
             is_deployment_in_progress: false,
             is_reset_in_progress: false,
             is_save_in_progress: false,
@@ -121,8 +117,8 @@ impl State {
         self.selected_mod_index = Some(index);
     }
 
-    pub fn add_mod(&mut self, info: ModInfo) {
-        if let Some(pos) = self.mods.index_of(&info) {
+    pub fn add_mod(&mut self, info: Arc<ModInfo>) {
+        if let Some(pos) = self.mods.iter().position(|i| i.id == info.id) {
             self.mods.set(pos, info);
             self.selected_mod_index = Some(pos);
         } else {
diff --git a/crates/dtmm/src/state/delegate.rs b/crates/dtmm/src/state/delegate.rs
index 08d17b0..6b05b96 100644
--- a/crates/dtmm/src/state/delegate.rs
+++ b/crates/dtmm/src/state/delegate.rs
@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use druid::{
     AppDelegate, Command, DelegateCtx, Env, FileInfo, Handled, Selector, SingleUse, Target,
 };
@@ -9,9 +11,9 @@ pub(crate) const ACTION_SELECT_MOD: Selector<usize> = Selector::new("dtmm.action
 pub(crate) const ACTION_SELECTED_MOD_UP: Selector = Selector::new("dtmm.action.selected-mod-up");
 pub(crate) const ACTION_SELECTED_MOD_DOWN: Selector =
     Selector::new("dtmm.action.selected-mod-down");
-pub(crate) const ACTION_START_DELETE_SELECTED_MOD: Selector<SingleUse<ModInfo>> =
+pub(crate) const ACTION_START_DELETE_SELECTED_MOD: Selector<SingleUse<Arc<ModInfo>>> =
     Selector::new("dtmm.action.srart-delete-selected-mod");
-pub(crate) const ACTION_FINISH_DELETE_SELECTED_MOD: Selector<SingleUse<ModInfo>> =
+pub(crate) const ACTION_FINISH_DELETE_SELECTED_MOD: Selector<SingleUse<Arc<ModInfo>>> =
     Selector::new("dtmm.action.finish-delete-selected-mod");
 
 pub(crate) const ACTION_START_DEPLOY: Selector = Selector::new("dtmm.action.start-deploy");
@@ -23,7 +25,7 @@ pub(crate) const ACTION_FINISH_RESET_DEPLOYMENT: Selector =
     Selector::new("dtmm.action.finish-reset-deployment");
 
 pub(crate) const ACTION_ADD_MOD: Selector<FileInfo> = Selector::new("dtmm.action.add-mod");
-pub(crate) const ACTION_FINISH_ADD_MOD: Selector<SingleUse<ModInfo>> =
+pub(crate) const ACTION_FINISH_ADD_MOD: Selector<SingleUse<Arc<ModInfo>>> =
     Selector::new("dtmm.action.finish-add-mod");
 
 pub(crate) const ACTION_LOG: Selector<SingleUse<String>> = Selector::new("dtmm.action.log");
@@ -33,11 +35,13 @@ pub(crate) const ACTION_START_SAVE_SETTINGS: Selector =
 pub(crate) const ACTION_FINISH_SAVE_SETTINGS: Selector =
     Selector::new("dtmm.action.finish-save-settings");
 
+pub(crate) const ACTION_SET_DIRTY: Selector = Selector::new("dtmm.action.set-dirty");
+
 pub(crate) enum AsyncAction {
     DeployMods(State),
     ResetDeployment(State),
     AddMod((State, FileInfo)),
-    DeleteMod((State, ModInfo)),
+    DeleteMod((State, Arc<ModInfo>)),
     SaveSettings(State),
 }
 
@@ -81,6 +85,7 @@ impl AppDelegate<State> for Delegate {
             }
             cmd if cmd.is(ACTION_FINISH_DEPLOY) => {
                 state.is_deployment_in_progress = false;
+                state.dirty = false;
                 Handled::Yes
             }
             cmd if cmd.is(ACTION_START_RESET_DEPLOYMENT) => {
@@ -165,7 +170,6 @@ impl AppDelegate<State> for Delegate {
                 };
 
                 state.mods.remove(index);
-                // ctx.submit_command(ACTION_START_SAVE_SETTINGS);
 
                 Handled::Yes
             }
@@ -188,7 +192,6 @@ impl AppDelegate<State> for Delegate {
                     .expect("command type matched but didn't contain the expected value");
                 if let Some(info) = info.take() {
                     state.add_mod(info);
-                    //     ctx.submit_command(ACTION_START_SAVE_SETTINGS);
                 }
                 Handled::Yes
             }
@@ -226,6 +229,10 @@ impl AppDelegate<State> for Delegate {
 
                 Handled::Yes
             }
+            cmd if cmd.is(ACTION_SET_DIRTY) => {
+                state.dirty = true;
+                Handled::Yes
+            }
             cmd => {
                 if cfg!(debug_assertions) {
                     tracing::warn!("Unknown command: {:?}", cmd);
diff --git a/crates/dtmm/src/state/lens.rs b/crates/dtmm/src/state/lens.rs
index 6c457a4..1156f52 100644
--- a/crates/dtmm/src/state/lens.rs
+++ b/crates/dtmm/src/state/lens.rs
@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use druid::im::Vector;
 use druid::{Data, Lens};
 
@@ -5,9 +7,9 @@ use super::{ModInfo, State};
 
 pub(crate) struct SelectedModLens;
 
-impl Lens<State, Option<ModInfo>> for SelectedModLens {
+impl Lens<State, Option<Arc<ModInfo>>> for SelectedModLens {
     #[tracing::instrument(name = "SelectedModLens::with", skip_all)]
-    fn with<V, F: FnOnce(&Option<ModInfo>) -> V>(&self, data: &State, f: F) -> V {
+    fn with<V, F: FnOnce(&Option<Arc<ModInfo>>) -> V>(&self, data: &State, f: F) -> V {
         let info = data
             .selected_mod_index
             .and_then(|i| data.mods.get(i).cloned());
@@ -16,16 +18,16 @@ impl Lens<State, Option<ModInfo>> for SelectedModLens {
     }
 
     #[tracing::instrument(name = "SelectedModLens::with_mut", skip_all)]
-    fn with_mut<V, F: FnOnce(&mut Option<ModInfo>) -> V>(&self, data: &mut State, f: F) -> V {
+    fn with_mut<V, F: FnOnce(&mut Option<Arc<ModInfo>>) -> V>(&self, data: &mut State, f: F) -> V {
         match data.selected_mod_index {
             Some(i) => {
                 let mut info = data.mods.get_mut(i).cloned();
                 let ret = f(&mut info);
 
-                if let Some(info) = info {
+                if let Some(new) = info {
                     // TODO: Figure out a way to check for equality and
                     // only update when needed
-                    data.mods.set(i, info);
+                    data.mods.set(i, new);
                 } else {
                     data.selected_mod_index = None;
                 }
diff --git a/crates/dtmm/src/ui/widget/controller.rs b/crates/dtmm/src/ui/widget/controller.rs
index ce18d5b..1bd7f6a 100644
--- a/crates/dtmm/src/ui/widget/controller.rs
+++ b/crates/dtmm/src/ui/widget/controller.rs
@@ -1,7 +1,7 @@
 use druid::widget::{Button, Controller, Scroll};
 use druid::{Data, Env, Event, EventCtx, Rect, UpdateCtx, Widget};
 
-use crate::state::{State, ACTION_START_SAVE_SETTINGS};
+use crate::state::{State, ACTION_SET_DIRTY, ACTION_START_SAVE_SETTINGS};
 
 pub struct DisabledButtonController;
 
@@ -57,11 +57,16 @@ impl<T: Data, W: Widget<T>> Controller<T, Scroll<T, W>> for AutoScrollController
     }
 }
 
-/// A controller that submits the command to save settings every time its widget's
-/// data changes.
-pub struct SaveSettingsController;
+macro_rules! compare_state_fields {
+    ($old:ident, $new:ident, $($field:ident),+) => {
+        $($old.$field != $new.$field) || +
+    }
+}
 
-impl<W: Widget<State>> Controller<State, W> for SaveSettingsController {
+/// A controller that tracks state changes for certain fields and submits commands to handle them.
+pub struct DirtyStateController;
+
+impl<W: Widget<State>> Controller<State, W> for DirtyStateController {
     fn update(
         &mut self,
         child: &mut W,
@@ -70,13 +75,14 @@ impl<W: Widget<State>> Controller<State, W> for SaveSettingsController {
         data: &State,
         env: &Env,
     ) {
-        // Only filter for the values that actually go into the settings file.
-        if old_data.mods != data.mods
-            || old_data.game_dir != data.game_dir
-            || old_data.data_dir != data.data_dir
-        {
+        if compare_state_fields!(old_data, data, mods, game_dir, data_dir) {
             ctx.submit_command(ACTION_START_SAVE_SETTINGS);
         }
+
+        if compare_state_fields!(old_data, data, mods, game_dir) {
+            ctx.submit_command(ACTION_SET_DIRTY);
+        }
+
         child.update(ctx, old_data, data, env)
     }
 }
diff --git a/crates/dtmm/src/ui/window/main.rs b/crates/dtmm/src/ui/window/main.rs
index a0ccaa2..d500610 100644
--- a/crates/dtmm/src/ui/window/main.rs
+++ b/crates/dtmm/src/ui/window/main.rs
@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use druid::im::Vector;
 use druid::lens;
 use druid::widget::{
@@ -15,7 +17,7 @@ use crate::state::{
     ACTION_START_RESET_DEPLOYMENT,
 };
 use crate::ui::theme;
-use crate::ui::widget::controller::{AutoScrollController, SaveSettingsController};
+use crate::ui::widget::controller::{AutoScrollController, DirtyStateController};
 use crate::ui::widget::PathBufFormatter;
 
 const TITLE: &str = "Darktide Mod Manager";
@@ -31,43 +33,48 @@ pub(crate) fn new() -> WindowDesc<State> {
 }
 
 fn build_top_bar() -> impl Widget<State> {
+    let mods_button = Button::new("Mods")
+        .on_click(|_ctx, state: &mut State, _env| state.current_view = View::Mods);
+
+    let settings_button = Button::new("Settings").on_click(|_ctx, state: &mut State, _env| {
+        state.current_view = View::Settings;
+    });
+
+    let deploy_button = {
+        Button::dynamic(|state: &State, _| {
+            let mut s = String::new();
+            if state.dirty {
+                s.push_str("! ");
+            }
+            s.push_str("Deploy Mods");
+            s
+        })
+        .on_click(|ctx, _state: &mut State, _env| {
+            ctx.submit_command(ACTION_START_DEPLOY);
+        })
+        .disabled_if(|data, _| data.is_deployment_in_progress || data.is_reset_in_progress)
+    };
+
+    let reset_button = Button::new("Reset Game")
+        .on_click(|ctx, _state: &mut State, _env| {
+            ctx.submit_command(ACTION_START_RESET_DEPLOYMENT);
+        })
+        .disabled_if(|data, _| data.is_deployment_in_progress || data.is_reset_in_progress);
+
     Flex::row()
         .must_fill_main_axis(true)
         .main_axis_alignment(MainAxisAlignment::SpaceBetween)
         .with_child(
             Flex::row()
-                .with_child(
-                    Button::new("Mods")
-                        .on_click(|_ctx, state: &mut State, _env| state.current_view = View::Mods),
-                )
+                .with_child(mods_button)
                 .with_default_spacer()
-                .with_child(
-                    Button::new("Settings").on_click(|_ctx, state: &mut State, _env| {
-                        state.current_view = View::Settings;
-                    }),
-                ),
+                .with_child(settings_button),
         )
         .with_child(
             Flex::row()
-                .with_child(
-                    Button::new("Deploy Mods")
-                        .on_click(|ctx, _state: &mut State, _env| {
-                            ctx.submit_command(ACTION_START_DEPLOY);
-                        })
-                        .disabled_if(|data, _| {
-                            data.is_deployment_in_progress || data.is_reset_in_progress
-                        }),
-                )
+                .with_child(deploy_button)
                 .with_default_spacer()
-                .with_child(
-                    Button::new("Reset Game")
-                        .on_click(|ctx, _state: &mut State, _env| {
-                            ctx.submit_command(ACTION_START_RESET_DEPLOYMENT);
-                        })
-                        .disabled_if(|data, _| {
-                            data.is_deployment_in_progress || data.is_reset_in_progress
-                        }),
-                ),
+                .with_child(reset_button),
         )
         .padding(theme::TOP_BAR_INSETS)
         .background(theme::TOP_BAR_BACKGROUND_COLOR)
@@ -77,9 +84,11 @@ fn build_top_bar() -> impl Widget<State> {
 
 fn build_mod_list() -> impl Widget<State> {
     let list = List::new(|| {
-        let checkbox =
-            Checkbox::new("").lens(lens!((usize, ModInfo, bool), 1).then(ModInfo::enabled));
-        let name = Label::raw().lens(lens!((usize, ModInfo, bool), 1).then(ModInfo::name));
+        let checkbox = Checkbox::new("")
+            .lens(lens!((usize, Arc<ModInfo>, bool), 1).then(ModInfo::enabled.in_arc()));
+
+        let name =
+            Label::raw().lens(lens!((usize, Arc<ModInfo>, bool), 1).then(ModInfo::name.in_arc()));
 
         Flex::row()
             .must_fill_main_axis(true)
@@ -109,8 +118,10 @@ fn build_mod_list() -> impl Widget<State> {
                 .collect::<Vector<_>>()
         },
         |state, infos| {
-            infos.into_iter().for_each(|(i, info, _)| {
-                state.mods.set(i, info);
+            infos.into_iter().for_each(|(i, new, _)| {
+                if state.mods.get(i).cloned() != Some(new.clone()) {
+                    state.mods.set(i, new);
+                }
             });
         },
     ));
@@ -142,12 +153,12 @@ fn build_mod_details_buttons() -> impl Widget<State> {
             .on_click(|_ctx, enabled: &mut bool, _env| {
                 *enabled = !(*enabled);
             })
-            .lens(ModInfo::enabled)
+            .lens(ModInfo::enabled.in_arc())
         },
         // TODO: Gray out
         || Button::new("Enable Mod"),
     )
-    .disabled_if(|info: &Option<ModInfo>, _env: &druid::Env| info.is_none())
+    .disabled_if(|info: &Option<Arc<ModInfo>>, _env: &druid::Env| info.is_none())
     .lens(State::selected_mod);
 
     let button_add_mod = Button::new("Add Mod").on_click(|ctx, _state: &mut State, _env| {
@@ -162,14 +173,14 @@ fn build_mod_details_buttons() -> impl Widget<State> {
     });
 
     let button_delete_mod = Button::new("Delete Mod")
-        .on_click(|ctx, data: &mut Option<ModInfo>, _env| {
+        .on_click(|ctx, data: &mut Option<Arc<ModInfo>>, _env| {
             if let Some(info) = data {
                 ctx.submit_command(
                     ACTION_START_DELETE_SELECTED_MOD.with(SingleUse::new(info.clone())),
                 );
             }
         })
-        .disabled_if(|info: &Option<ModInfo>, _env: &druid::Env| info.is_none())
+        .disabled_if(|info: &Option<Arc<ModInfo>>, _env: &druid::Env| info.is_none())
         .lens(State::selected_mod);
 
     Flex::column()
@@ -203,10 +214,10 @@ fn build_mod_details_info() -> impl Widget<State> {
                 // Force the label to take up the entire details' pane width,
                 // so that we can center-align it.
                 .expand_width()
-                .lens(ModInfo::name);
+                .lens(ModInfo::name.in_arc());
             let description = Label::raw()
                 .with_line_break_mode(LineBreaking::WordWrap)
-                .lens(ModInfo::description);
+                .lens(ModInfo::description.in_arc());
 
             Flex::column()
                 .cross_axis_alignment(CrossAxisAlignment::Start)
@@ -312,5 +323,5 @@ fn build_window() -> impl Widget<State> {
         .with_child(build_top_bar())
         .with_flex_child(build_main(), 1.0)
         .with_child(build_log_view())
-        .controller(SaveSettingsController)
+        .controller(DirtyStateController)
 }
diff --git a/crates/dtmm/src/util/config.rs b/crates/dtmm/src/util/config.rs
index 86812b3..2c942ea 100644
--- a/crates/dtmm/src/util/config.rs
+++ b/crates/dtmm/src/util/config.rs
@@ -1,5 +1,6 @@
 use std::io::ErrorKind;
 use std::path::PathBuf;
+use std::sync::Arc;
 use std::{fs, path::Path};
 
 use clap::{parser::ValueSource, ArgMatches};
@@ -38,6 +39,7 @@ impl<'a> From<&'a State> for ConfigSerialize<'a> {
             mod_order: state
                 .mods
                 .iter()
+                .map(Arc::as_ref)
                 .map(LoadOrderEntrySerialize::from)
                 .collect(),
         }